An organization should choose its information technology (IT) strategy on all the data centers it uses so that it provides the right amount of reliability needed by the organization's IT applications. This means striking the best attainable balance between cost of strategy implementation and value it provides. A comprehensive assessment should combine factors such as the particular needs of the organization, such as application uptime needed, physical factors such as quality of data center designs and operations, implications of their geographical locations, effect of various sources of uncertainties, and other factors.
Redundancy is a reliability measure that an organization may implement to provide fail-safe facilities. In IT, redundancy implementation may involve providing duplicate components such as backup systems or minor systems. Existing practice defines redundancy in terms of Tiers (I-IV) applicable to individual data centers. Each Tier of redundancy matches a set of criteria for the reliability of operations, which include the average expected uptime in a year, the number of outage events expected, the severity of the average outage, etc. For example, Tier III operations promise an uptime of 99%, while Tier II updates this to 99.9% and Tier Ito 99.99%. While this approach narrows and simplifies the design choices of individual data centers, decisions on combining one or more data centers to support the substantial business computing needs of a firm are made in an ad-hoc manner without the benefit of a rational analysis of the cost of the redundancy defined by a tier and the quantified resilience it provides to the business. They provide no ability to identify any data center strategy's value to the particular needs of an organization. The current metrics used for understanding reliability generally do not facilitate the business decision of understanding the value of availability of the redundancy or resiliency.